MANUAL OF ELEMENTARY ZOOLOGY 



The formation of a pseudopodium begins with a slight 

 outflowing of the ectoplasm, into which the 

 endoplasm presently flows. The projection 

 continues to grow by the flow of more protoplasm into it 

 for a varying time, and locomotion is brought about by 

 the persistent lengthening of one pseudopodium till the 

 bulk of the body has been transferred into it. During 

 this time it is throwing out subsidiary pseudopodia 

 in various directions. Before very long, however, the 

 main flow is directed into one of these and the animal 



FIG. 68. — Amoeba proteus, highly magnified. 



c.v., Contractile vacuole ; ec, ectoplasm ; en. } endoplasm ;f.p., food particles ; 

 nu., nucleus ; ps., pseudopodia. 



moves in another direction, the stream in the older pseudo- 

 podia setting backward into the body until they disappear. 

 The flow of the endoplasm is always swifter in the middle of 

 a pseudopodium than at the sides. It will be seen that we 

 have here an example of contraction, as the word is used in 

 Biology, the shape of the mass of protoplasm being changed 

 by the transference of material, but the size remaining 

 the same. The throwing out of a pseudopodium is not 

 brought about merely by a flowing of the protoplasm. The 

 ectoplasm has a certain toughness and its surface is sticky. 

 After the first outflow of ectoplasm has begun to form the 

 pseudopodium, as the endoplasm flows into it, the ecto- 



